User equipment (UE) capability on secondary cell (SCell) beam failure recovery (BFR)

ABSTRACT

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for wireless communications by a user equipment (UE). Embodiments include reporting, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). Embodiments include detecting a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. Embodiments include performing a BFR in accordance with the reported capability, in response to the detection.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/971,035, filed Feb. 6, 2020, herein incorporated by reference in its entirety as if fully set forth below and for all applicable purposes.

INTRODUCTION

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for signaling user equipment (UE) capability on secondary cell (SCell) beam failure recovery (BFR).

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

In some examples, a wireless multiple-access communication system may include a number of base stations (BSs), which are each capable of simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). In an LTE or LTE-A network, a set of one or more base stations may define an eNodeB (eNB). In other examples (e.g., in a next generation, a new radio (NR), or 5G network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more distributed units, in communication with a central unit, may define an access node (e.g., which may be referred to as a base station, 5G NB, next generation NodeB (gNB or gNodeB), TRP, etc.). A base station or distributed unit may communicate with a set of UEs on downlink channels (e.g., for transmissions from a base station or to a UE) and uplink channels (e.g., for transmissions from a UE to a base station or distributed unit).

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. New Radio (NR) (e.g., 5G) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL). To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

BRIEF SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved communications between access points and stations in a wireless network.

Certain aspects provide a method for wireless communication performed by a user equipment (UE). The method generally includes reporting, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The method further includes detecting a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The method further includes performing a BFR in accordance with the reported capability, in response to the detection.

Certain aspects of the present disclosure provide a method for wireless communication by a network entity. The method generally includes receiving, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The method further includes receiving, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The method further includes taking action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure.

Certain aspects provide an apparatus for wireless communication by a user equipment (UE). The apparatus may comprise a memory and a processor coupled to the memory. The memory and processor may be configured to report, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The memory and processor may be further configured to detect a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The memory and processor may be further configured to take action to perform a BFR in accordance with the reported capability, in response to the detection.

Certain aspects provide an apparatus for wireless communication by a network entity. The apparatus may comprise a memory and a processor coupled to the memory. The memory and processor may be configured to receive, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The memory and processor may be further configured to receive, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The memory and processor may be further configured to take action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure.

Certain aspects provide an apparatus for wireless communication performed by a user equipment (UE). The apparatus generally includes means for reporting, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The apparatus further includes means for detecting a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The apparatus further includes means for performing a BFR in accordance with the reported capability, in response to the detection.

Certain aspects of the present disclosure provide an apparatus for wireless communication by a network entity. The apparatus generally includes means for receiving, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The apparatus further includes means for receiving, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The apparatus further includes means for taking action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure.

Certain aspects can be implemented in a non-transitory computer-readable medium for wireless communication by a user equipment (UE). The non-transitory computer-readable medium may comprise computer-executable instructions that, when executed by one or more processors of a processing system, cause the processing system to report, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The computer-executable instructions, when executed by the one or more processors of the processing system, further cause the processing system to detect a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The computer-executable instructions, when executed by the one or more processors of the processing system, further cause the processing system to take action to perform a BFR in accordance with the reported capability, in response to the detection.

Certain aspects can be implemented in a non-transitory computer-readable medium for wireless communication by a user equipment (UE). The non-transitory computer-readable medium may comprise computer-executable instructions that, when executed by one or more processors of a processing system, cause the processing system to receive, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells). The computer-executable instructions, when executed by the one or more processors of the processing system, further cause the processing system to receive, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells. The computer-executable instructions, when executed by the one or more processors of the processing system, further cause the processing system to take action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure.

Aspects of the present disclosure provide means for, apparatus, processors, and computer-readable mediums for performing the methods described herein.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims.

While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, packaging arrangements. For example, embodiments and/or uses may come about via integrated chip embodiments and other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, AI-enabled devices, etc.). While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described innovations may occur. Implementations may range in spectrum from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregate, distributed, or OEM devices or systems incorporating one or more aspects of the described innovations. In some practical settings, devices incorporating described aspects and features may also necessarily include additional components and features for implementation and practice of claimed and described embodiments. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor(s), interleaver, adders/summers, etc.). It is intended that innovations described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, end-user devices, etc. of varying sizes, shapes, and constitution.

The following description and the appended figures set forth certain features for purposes of illustration.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram illustrating an example logical architecture of a distributed radio access network (RAN), in accordance with certain aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example physical architecture of a distributed RAN, in accordance with certain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating a design of an example base station (BS) and user equipment (UE), in accordance with certain aspects of the present disclosure.

FIG. 5 is a diagram showing examples for implementing a communication protocol stack, in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates an example of a frame format for a new radio (NR) system.

FIG. 7 illustrates how different synchronization signal blocks (SSBs) may be sent using different beams, in accordance with certain aspects of the present disclosure.

FIG. 8 shows an exemplary transmission resource mapping, according to aspects of the present disclosure.

FIG. 9 illustrates example quasi co-location (QCL) relationships.

FIG. 10 illustrates example operations for wireless communication by a UE, in accordance with some aspects of the present disclosure.

FIG. 11 illustrates example operations for wireless communication by a network entity, in accordance with some aspects of the present disclosure.

FIG. 12 is a call flow diagram illustrating example operations for signaling UE capability for SCell BFR.

FIG. 13 illustrates example UE capability signaling for SCell BFR.

FIG. 14 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

FIG. 15 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for signaling user equipment (UE) capability on secondary cell (SCell) beam failure recovery (BFR).

The following description provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

The techniques described herein may be used for various wireless communication technologies, such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as NR (e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS).

New Radio (NR) is an emerging wireless communications technology under development in conjunction with the 5G Technology Forum (5GTF). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

New radio (NR) access (e.g., 5G technology) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., 25 GHz or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe.

Example Wireless Communications System

FIG. 1 illustrates an example wireless communication network 100 (e.g., an NR/5G network), in which aspects of the present disclosure may be performed. For example, the wireless network 100 may include a UE 120 configured to perform operations 1000 of FIG. 10 for signaling user equipment (UE) capability for secondary cell (SCell) beam failure recovery (BFR). Similarly, a base station 110 (e.g., a gNB) may be configured to perform operations 1100 of FIG. 11 related to receiving signaling of UE capability for SCell BFR.

As illustrated in FIG. 1 , the wireless network 100 may include a number of base stations (BSs) 110 and other network entities. A BS may be a station that communicates with user equipments (UEs). Each BS 110 may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a NodeB (NB) and/or a NodeB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and next generation NodeB (gNB), new radio base station (NR BS), 5G NB, access point (AP), or transmission reception point (TRP) may be interchangeable. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some examples, the base stations may be interconnected to one another and/or to one or more other base stations or network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces, such as a direct physical connection, a wireless connection, a virtual network, or the like using any suitable transport network.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

A base station (BS) may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in the home, etc.). A BS for a macro cell may be referred to as a macro BS. ABS for a pico cell may be referred to as a pico BS. ABS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in FIG. 1 , the BSs 110 a, 110 b and 110 c may be macro BSs for the macro cells 102 a, 102 b and 102 c, respectively. The BS 110 x may be a pico BS for a pico cell 102 x. The BSs 110 y and 110 z may be femto BSs for the femto cells 102 y and 102 z, respectively. A BS may support one or multiple (e.g., three) cells.

Wireless communication network 100 may also include relay stations. A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., a BS or a UE) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or a BS). A relay station may also be a UE that relays transmissions for other UEs. In the example shown in FIG. 1 , a relay station 110 r may communicate with the BS 110 a and a UE 120 r to facilitate communication between the BS 110 a and the UE 120 r. A relay station may also be referred to as a relay BS, a relay, etc.

Wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network 100. For example, macro BS may have a high transmit power level (e.g., 20 Watts) whereas pico BS, femto BS, and relays may have a lower transmit power level (e.g., 1 Watt).

Wireless communication network 100 may support synchronous or asynchronous operation. For synchronous operation, the BSs may have similar frame timing, and transmissions from different BSs may be approximately aligned in time. For asynchronous operation, the BSs may have different frame timing, and transmissions from different BSs may not be aligned in time. The techniques described herein may be used for both synchronous and asynchronous operation.

A network controller 130 may couple to a set of BSs and provide coordination and control for these BSs. The network controller 130 may communicate with the BSs 110 via a backhaul. The BSs 110 may also communicate with one another (e.g., directly or indirectly) via wireless or wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout the wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE), a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a satellite radio, etc.), a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, gaming device, reality augmentation device (augmented reality (AR), extended reality (XR), or virtual reality (VR)), or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (e.g., remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a “resource block” (RB)) may be 12 subcarriers (or 180 kHz). Consequently, the nominal Fast Fourier Transfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e., 6 resource blocks), and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communications systems, such as NR. NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells.

In some scenarios, air interface access may be scheduled. For example, a scheduling entity (e.g., a base station (BS), Node B, eNB, gNB, or the like) can allocate resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities can utilize resources allocated by one or more scheduling entities.

Base stations are not the only entities that may function as a scheduling entity. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs), and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may communicate directly with one another in addition to communicating with a scheduling entity.

Turning back to FIG. 1 , this figure illustrates a variety of potential deployments for various deployment scenarios. For example, in FIG. 1 , a solid line with double arrows indicates desired transmissions between a UE and a serving BS, which is a BS designated to serve the UE on the downlink and/or uplink. A finely dashed line with double arrows indicates interfering transmissions between a UE and a BS. Other lines show component to component (e.g., UE to UE) communication options.

FIG. 2 illustrates an example logical architecture of a distributed Radio Access Network (RAN) 200, which may be implemented in the wireless communication network 100 illustrated in FIG. 1 . A 5G access node 206 may include an access node controller (ANC) 202. ANC 202 may be a central unit (CU) of the distributed RAN 200. The backhaul interface to the Next Generation Core Network (NG-CN) 204 may terminate at ANC 202. The backhaul interface to neighboring next generation access Nodes (NG-ANs) 210 may terminate at ANC 202. ANC 202 may include one or more transmission reception points (TRPs) 208 (e.g., cells, BSs, gNBs, etc.).

The TRPs 208 may be a distributed unit (DU). TRPs 208 may be connected to a single ANC (e.g., ANC 202) or more than one ANC (not illustrated). For example, for RAN sharing, radio as a service (RaaS), and service specific ANC deployments, TRPs 208 may be connected to more than one ANC. TRPs 208 may each include one or more antenna ports. TRPs 208 may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

The logical architecture of distributed RAN 200 may support various backhauling and fronthauling solutions. This support may occur via and across different deployment types. For example, the logical architecture may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter).

The logical architecture of distributed RAN 200 may share features and/or components with LTE. For example, next generation access node (NG-AN) 210 may support dual connectivity with NR and may share a common fronthaul for LTE and NR.

The logical architecture of distributed RAN 200 may enable cooperation between and among TRPs 208, for example, within a TRP and/or across TRPs via ANC 202. An inter-TRP interface may not be used.

Logical functions may be dynamically distributed in the logical architecture of distributed RAN 200. As will be described in more detail with reference to FIG. 5 , the Radio Resource Control (RRC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and a Physical (PHY) layers may be adaptably placed at the DU (e.g., TRP 208) or CU (e.g., ANC 202).

FIG. 3 illustrates an example physical architecture of a distributed Radio Access Network (RAN) 300, according to aspects of the present disclosure. A centralized core network unit (C-CU) 302 may host core network functions. C-CU 302 may be centrally deployed. C-CU 302 functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions. Optionally, the C-RU 304 may host core network functions locally. The C-RU 304 may have distributed deployment. The C-RU 304 may be close to the network edge.

A DU 306 may host one or more TRPs (Edge Node (EN), an Edge Unit (EU), a Radio Head (RH), a Smart Radio Head (SRH), or the like). The DU may be located at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of BS 110 and UE 120 (as depicted in FIG. 1 ), which may be used to implement aspects of the present disclosure. For example, antennas 452, processors 466, 458, 464, and/or controller/processor 480 of the UE 120 may be used to perform operations 1000 of FIG. 10 , while antennas 434, processors 420, 460, 438, and/or controller/processor 440 of the BS 110 may be used to perform operations 1100 of FIG. 11 .

At the BS 110, a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440. The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data may be for the physical downlink shared channel (PDSCH), etc. The processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor 420 may also generate reference symbols, e.g., for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and cell-specific reference signal (CRS). A transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432 a through 432 t. Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 432 a through 432 t may be transmitted via the antennas 434 a through 434 t, respectively.

At the UE 120, antennas 452 a through 452 r may receive downlink signals from the base station 110 and may provide received signals to demodulators (DEMODs) in transceivers 454 a through 454 r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, down convert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 456 may obtain received symbols from all demodulators 454 a through 454 r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 to a data sink 460, and provide decoded control information to a controller/processor 480.

On the uplink, at UE 120, a transmit processor 464 may receive and process data (e.g., for the physical uplink shared channel (PUSCH)) from a data source 462 and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor 480. The transmit processor 464 may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS)). The symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the demodulators in transceivers 454 a through 454 r (e.g., for SC-FDM, etc.), and transmitted to the base station 110. At the BS 110, uplink signals from the UE 120 may be received by the antennas 434, processed by the modulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 120. The receive processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440.

The controllers/processors 440 and 480 may direct operations at the base station 110 and the UE 120, respectively. The processor 440 and/or other processors and modules at the BS 110 may perform or direct execution of processes for techniques described herein. The memories 442 and 482 may store data and program codes for BS 110 and UE 120, respectively. A scheduler 444 may schedule UEs for data transmission on the downlink and/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing a communications protocol stack, according to aspects of the present disclosure. The illustrated communications protocol stacks may be implemented by devices operating in a wireless communication system, such as a 5G system (e.g., a system that supports uplink-based mobility). Diagram 500 illustrates a communications protocol stack including a Radio Resource Control (RRC) layer 510, a Packet Data Convergence Protocol (PDCP) layer 515, a Radio Link Control (RLC) layer 520, a Medium Access Control (MAC) layer 525, and a Physical (PHY) layer 530. In various examples, the layers of a protocol stack may be implemented as separate modules of software, portions of a processor or ASIC, portions of non-collocated devices connected by a communications link, or various combinations thereof. Collocated and non-collocated implementations may be used, for example, in a protocol stack for a network access device (e.g., ANs, CUs, and/or DUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack, in which implementation of the protocol stack is split between a centralized network access device (e.g., an ANC 202 in FIG. 2 ) and distributed network access device (e.g., DU 208 in FIG. 2 ). In the first option 505-a, an RRC layer 510 and a PDCP layer 515 may be implemented by the central unit, and an RLC layer 520, a MAC layer 525, and a PHY layer 530 may be implemented by the DU. In various examples the CU and the DU may be collocated or non-collocated. The first option 505-a may be useful in a macro cell, micro cell, or pico cell deployment.

A second option 505-b shows a unified implementation of a protocol stack, in which the protocol stack is implemented in a single network access device. In the second option, RRC layer 510, PDCP layer 515, RLC layer 520, MAC layer 525, and PHY layer 530 may each be implemented by the AN. The second option 505-b may be useful in, for example, a femto cell deployment.

Regardless of whether a network access device implements part or all of a protocol stack, a UE may implement an entire protocol stack as shown in 505-c (e.g., the RRC layer 510, the PDCP layer 515, the RLC layer 520, the MAC layer 525, and the PHY layer 530).

Embodiments discussed herein may include a variety of spacing and timing deployments. For example, in LTE, the basic transmission time interval (TTI) or packet duration is the 1 ms subframe. In NR, a subframe is still 1 ms, but the basic TTI is referred to as a slot. A subframe contains a variable number of slots (e.g., 1, 2, 4, 8, 16, slots) depending on the subcarrier spacing. The NR RB is 12 consecutive frequency subcarriers. NR may support a base subcarrier spacing of 15 KHz and other subcarrier spacing may be defined with respect to the base subcarrier spacing, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing.

FIG. 6 is a diagram showing an example of a frame format 600 for NR. The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be partitioned into 10 subframes, each of 1 ms, with indices of 0 through 9. Each subframe may include a variable number of slots depending on the subcarrier spacing. Each slot may include a variable number of symbol periods (e.g., 7 or 14 symbols) depending on the subcarrier spacing. The symbol periods in each slot may be assigned indices. A mini-slot is a subslot structure (e.g., 2, 3, or 4 symbols).

Each symbol in a slot may indicate a link direction (e.g., DL, UL, or flexible) for data transmission and the link direction for each subframe may be dynamically switched. The link directions may be based on the slot format. Each slot may include DL/UL data as well as DL/UL control information.

In NR, a synchronization signal (SS) block (SSB) is transmitted. The SS block includes a PSS, a SSS, and a two symbol PBCH. The SS block can be transmitted in a fixed slot location, such as the symbols 0-3 as shown in FIG. 6 . The PSS and SSS may be used by UEs for cell search and acquisition. The PSS may provide half-frame timing, and the SS may provide the CP length and frame timing. The PSS and SSS may provide the cell identity. The PBCH carries some basic system information, such as downlink system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc.

Further system information such as, remaining minimum system information (RMSI), system information blocks (SIBs), other system information (OSI) can be transmitted on a physical downlink shared channel (PDSCH) in certain subframes.

As shown in FIG. 7 , the SS blocks may be organized into SS burst sets to support beam sweeping. As shown, each SSB within a burst set may be transmitted using a different beam, which may help a UE quickly acquire both transmit (Tx) and receive (Rx) beams (particular for mmW applications). A physical cell identity (PCI) may still decoded from the PSS and SSS of the SSB.

Certain deployment scenarios may include one or both NR deployment options. Some may be configured for non-standalone (NSA) and/or standalone (SA) option. A standalone cell may need to broadcast both SSB and remaining minimum system information (RMSI), for example, with SIB1 and SIB2. A non-standalone cell may only need to broadcast SSB, without broadcasting RMSI. In a single carrier in NR, multiple SSBs may be sent in different frequencies, and may include the different types of SSB.

Control Resource Sets (CORESETs)

A control resource set (CORESET) for an OFDMA system (e.g., a communications system transmitting PDCCH using OFDMA waveforms) may comprise one or more control resource (e.g., time and frequency resources) sets, configured for conveying PDCCH, within the system bandwidth. Within each CORESET, one or more search spaces (e.g., common search space (CSS), UE-specific search space (USS), etc.) may be defined for a given UE. Search spaces are generally areas or portions where a communication device (e.g., a UE) may look for control information.

According to aspects of the present disclosure, a CORESET is a set of time and frequency domain resources, defined in units of resource element groups (REGs). Each REG may comprise a fixed number (e.g., twelve) tones in one symbol period (e.g., a symbol period of a slot), where one tone in one symbol period is referred to as a resource element (RE). A fixed number of REGs may be included in a control channel element (CCE). Sets of CCEs may be used to transmit new radio PDCCHs (NR-PDCCHs), with different numbers of CCEs in the sets used to transmit NR-PDCCHs using differing aggregation levels. Multiple sets of CCEs may be defined as search spaces for UEs, and thus a NodeB or other base station may transmit an NR-PDCCH to a UE by transmitting the NR-PDCCH in a set of CCEs that is defined as a decoding candidate within a search space for the UE, and the UE may receive the NR-PDCCH by searching in search spaces for the UE and decoding the NR-PDCCH transmitted by the NodeB.

Operating characteristics of a NodeB or other base station in an NR communications system may be dependent on a frequency range (FR) in which the system operates. A frequency range may comprise one or more operating bands (e.g., “n1” band, “n2” band, “n7” band, and “n41” band), and a communications system (e.g., one or more NodeBs and UEs) may operate in one or more operating bands. Frequency ranges and operating bands are described in more detail in “Base Station (BS) radio transmission and reception” TS38.104 (Release 15), which is available from the 3GPP website.

As described above, a CORESET is a set of time and frequency domain resources. The CORESET can be configured for conveying PDCCH within system bandwidth. A UE may determine a CORESET and monitors the CORESET for control channels. During initial access, a UE may identify an initial CORESET (CORESET #0) configuration from a field (e.g., pdcchConfigSIB1) in a master information block (MIB). This initial CORESET may then be used to configure the UE (e.g., with other CORESETs and/or bandwidth parts via dedicated (UE-specific) signaling). When the UE detects a control channel in the CORESET, the UE attempts to decode the control channel and communicates with the transmitting BS (e.g., the transmitting cell) according to the control data provided in the control channel (e.g., transmitted via the CORESET).

According to aspects of the present disclosure, when a UE is connected to a cell (or BS), the UE may receive a MIB. The MIB can be in a synchronization signal and physical broadcast channel (SS/PBCH) block (e.g., in the PBCH of the SS/PBCH block) on a synchronization raster (sync raster). In some scenarios, the sync raster may correspond to an SSB. From the frequency of the sync raster, the UE may determine an operating band of the cell. Based on a cell's operation band, the UE may determine a minimum channel bandwidth and a subcarrier spacing (SCS) of the channel. The UE may then determine an index from the MIB (e.g., four bits in the MIB, conveying an index in a range 0-15).

Given this index, the UE may look up or locate a CORESET configuration (this initial CORESET configured via the MIB is generally referred to as CORESET #0). This may be accomplished from one or more tables of CORESET configurations. These configurations (including single table scenarios) may include various subsets of indices indicating valid CORESET configurations for various combinations of minimum channel bandwidth and SCS. In some arrangements, each combination of minimum channel bandwidth and SCS may be mapped to a subset of indices in the table.

Alternatively or additionally, the UE may select a search space CORESET configuration table from several tables of CORESET configurations. These configurations can be based on a minimum channel bandwidth and SCS. The UE may then look up a CORESET configuration (e.g., a TypeO-PDCCH search space CORESET configuration) from the selected table, based on the index. After determining the CORESET configuration (e.g., from the single table or the selected table), the UE may then determine the CORESET to be monitored (as mentioned above) based on the location (in time and frequency) of the SS/PBCH block and the CORESET configuration.

FIG. 8 shows an exemplary transmission resource mapping 800, according to aspects of the present disclosure. In the exemplary mapping, a BS (e.g., BS 110 a, shown in FIG. 1 ) transmits an SS/PBCH block 802. The SS/PBCH block 802 includes a MIB conveying an index to a table that relates the time and frequency resources of the CORESET 804 to the time and frequency resources of the SS/PBCH block 802.

The BS may also transmit control signaling. In some scenarios, the BS may also transmit a PDCCH to a UE (e.g., UE 120, shown in FIG. 1 ) in the (time/frequency resources of the) CORESET. The PDCCH may schedule a PDSCH 806. The BS then transmits the PDSCH 806 to the UE. The UE may receive the MIB in the SS/PBCH block 802, determine the index, look up a CORESET configuration based on the index, and determine the CORESET from the CORESET configuration and the SS/PBCH block 802. The UE may then monitor the CORESET, decode the PDCCH in the CORESET, and receive the PDSCH that was allocated by the PDCCH.

Different CORESET configurations may have different parameters that define a corresponding CORESET. For example, each configuration may indicate a number of resource blocks (e.g., 24, 48, or 96), a number of symbols (e.g., 1-3), as well as an offset (e.g., 0-38 RBs) that indicates a location in frequency.

QCL Port and TCI States

In many cases, it is important for a UE to know which assumptions it can make on a channel corresponding to different transmissions. For example, the UE may need to know which reference signals it can use to estimate the channel in order to decode a transmitted signal (e.g., PDCCH or PDSCH). It may also be important for the UE to be able to report relevant channel state information (CSI) to the BS (gNB) for scheduling, link adaptation, and/or beam management purposes. In NR, the concept of quasi co-location (QCL) and transmission configuration indicator (TCI) states is used to convey information about these assumptions.

QCL assumptions are generally defined in terms of channel properties. Per 3GPP TS 38.214, “two antenna ports are said to be quasi-co-located if properties of the channel over which a symbol on one antenna port is conveyed can be inferred from the channel over which a symbol on the other antenna port is conveyed.” Different reference signals may be considered quasi co-located (“QCL′ d”) if a receiver (e.g., a UE) can apply channel properties determined by detecting a first reference signal to help detect a second reference signal. TCI states generally include configurations such as QCL-relationships, for example, between the DL RSs in one CSI-RS set and the PDSCH DMRS ports.

In some cases, a UE may be configured with up to M TCI-States. Configuration of the M TCI-States can come about via higher layer signalling, while a UE may be signalled to decode PDSCH according to a detected PDCCH with DCI indicating one of the TCI states. Each configured TCI state may include one RS set TCI-RS-SetConfig that indicates different QCL assumptions between certain source and target signals.

FIG. 9 illustrate examples of the association of DL reference signals with corresponding QCL types that may be indicated by a TCI-RS-SetConfig.

In the examples of FIG. 9 , a source reference signal (RS) is indicated in the top block and is associated with a target signal indicated in the bottom block. In this context, a target signal generally refers to a signal for which channel properties may be inferred by measuring those channel properties for an associated source signal. As noted above, a UE may use the source RS to determine various channel parameters, depending on the associated QCL type, and use those various channel properties (determined based on the source RS) to process the target signal. A target RS does not necessarily need to be PDSCH's DMRS, rather it can be any other RS: PUSCH DMRS, CSIRS, TRS, and SRS.

As illustrated, each TCI-RS-SetConfig contains parameters. These parameters can, for example, configure quasi co-location relationship(s) between reference signals in the RS set and the DM-RS port group of the PDSCH. The RS set contains a reference to either one or two DL RSs and an associated quasi co-location type (QCL-Type) for each one configured by the higher layer parameter QCL-Type.

As illustrated in FIG. 9 , for the case of two DL RSs, the QCL types can take on a variety of arrangements. For example, QCL types may not be the same, regardless of whether the references are to the same DL RS or different DL RSs. In the illustrated example, SSB is associated with Type C QCL for P-TRS, while CSI-RS for beam management (CSIRS-BM) is associated with Type D QCL.

QCL information and/or types may in some scenarios depend on or be a function of other information. For example, the quasi co-location (QCL) types indicated to the UE can be based on higher layer parameter QCL-Type and may take one or a combination of the following types:

QCL-TypeA: {Doppler shift, Doppler spread, average delay, delay spread},

QCL-TypeB: {Doppler shift, Doppler spread},

QCL-TypeC: {average delay, Doppler shift}, and

QCL-TypeD: {Spatial Rx parameter},

Spatial QCL assumptions (QCL-TypeD) may be used to help a UE to select an analog Rx beam (e.g., during beam management procedures). For example, an SSB resource indicator may indicate a same beam for a previous reference signal should be used for a subsequent transmission.

An initial CORESET (e.g., CORESET ID 0 or simply CORESET #0) in NR may be identified during initial access by a UE (e.g., via a field in the MIB). A ControlResourceSet information element (CORESET IE) sent via radio resource control (RRC) signaling may convey information regarding a CORESET configured for a UE. The CORESET IE generally includes a CORESET ID, an indication of frequency domain resources (e.g., number of RBs) assigned to the CORESET, contiguous time duration of the CORESET in a number of symbols, and Transmission Configuration Indicator (TCI) states.

As noted above, a subset of the TCI states provide quasi co-location (QCL) relationships between DL RS(s) in one RS set (e.g., TCI-Set) and PDCCH demodulation RS (DMRS) ports. A particular TCI state for a given UE (e.g., for unicast PDCCH) may be conveyed to the UE by the Medium Access Control (MAC) Control Element (MAC-CE). The particular TCI state is generally selected from the set of TCI states conveyed by the CORESET IE, with the initial CORESET (CORESET #0) generally configured via MIB.

Search space information may also be provided via RRC signaling. For example, the Search Space IE is another RRC IE that defines how and where to search for PDCCH candidates for a given CORESET. Each search space is associated with one CORESET. The Search Space IE identifies a search space configured for a CORESET by a search space ID. In an aspect, the search space ID associated with CORESET #0 is Search Space ID #0. The search space is generally configured via PBCH (MIB).

Example Techniques for UE Capability Signaling Regarding SCell BFR

Certain systems, such as NR, support carrier aggregation (CA). With CA, the UE can use multiple carriers/cells to communicate with a BS (or multiple BSs). CA involves a primary cell (Pcell) and at least one secondary cell (Scell). An Scell may be configured for downlink only, or configured for both uplink and downlink.

The Pcell and Scell(s) can be in different frequency bands. For example, Frequency Range 1 (FR1) includes, for example, sub-6 GHz frequency bands, while Frequency Range 2 (FR2) includes, for example, frequency bands from 24.25 GHz to 52.6 GHz. In an embodiment, a Pcell is in one frequency range (e.g., FR1, sub-6 GHz) and the Scell is in another frequency range (FR2, 28 GHz).

The Pcell and Scell may use different tone spacing or subcarrier spacing (SCS), leading to different symbol lengths for the Pcell and Scell(s). For example, in FR2 the symbols length for a 120 KHz SCS is eight times short than a symbol length for a 15 kHz SCS in FR1.

In FR2 (mmW communications), directional beamforming may be used between the UE and gNB. As such, the UE and gNB communicate via a beam pair link (BPL), which may be a corresponding transmit beam and receive beam on each side of the communication. In some cases, the UE can detect beam failure (e.g. RSRP of BPL is bad), and send beam failure recovery request (BFRQ) to the gNB. Such BFR process can be cell-specific (e.g., there can be PCell BFR and SCell BFR).

As mentioned above, aspects of the present disclosure relate beam failure detection and recovery. In some systems, narrow-beam transmission and reception is useful for improving the link budget at millimeter-wave (mmW) frequencies but may be susceptible to beam failure. In mmW, directional beamforming is used between the UE and a BS, and the UE and BS communicate via a beam pair link (BPL). A beam failure generally refers to a scenario in which the quality of a beam falls below a threshold, which may lead to radio link failure (RLF). NR supports a lower layer signaling to recover from beam failure, referred to as beam recovery. For example, instead of initiating a cell reselection when a beam quality becomes too low, a beam pair reselection within the cell may be performed.

Beam failure may be detected by monitoring a beam failure detection (BFD) reference signal (RS) and assessing if a beam failure trigger condition has been met. A UE may monitor the BFD RS from an Scell. In some examples, beam failure detection is triggered if an estimated block error rate (BLER) of reference signals associated with a configured control resource set (CORESET) is above a threshold (e.g., 10%). In some examples, the UE detects beam failure when the reference signal receive power (RSRP) of a BPL is below a threshold.

To recover the Scell, the UE can send a beam failure request (BFRQ) message on another cell. In some examples, the BFRQ is sent on the Pcell. In NR systems, a two-step BFRQ may be used. The BFRQ may request a new transmission. After detecting beam failure, the UE may send the first step (or first stage) of the BFRQ. The first step of the BFRQ message may include a scheduling request (SR) on the Pcell. The SR may be sent on dedicated SR resources. The SR may request scheduling for the second step (or second stage) of the BFRQ message. The UE may receive a PDCCH from the Pcell, in response to the SR, scheduling the second set of the BFRQ message. The UE then sends the scheduled second step of the BFRQ message on the Pcell. For example, the UE sends a PUSCH including a MAC-CE. The MAC-CE may include, in some embodiments, an index of the failed CC and a new recovery beam candidate beam. In some examples, to find candidate new beams, the UE may monitor a beam identification reference signal.

The Pcell responds to the BFRQ by transmitting a beam failure recovery response (BFRR) message to the UE. The BFRR message may acknowledge the MAC-CE and include an uplink grant scheduling a new transmission. For example, the uplink grant may schedule a transmission for the same HARQ process as the PUSCH carrying the MAC-CE in the step two of the BFRQ. In some examples, the BFRR is sent over a CORESET (e.g., referred to as a CORESET-BFR) the UE monitors for the response.

If the response is received successfully, the beam recovery is completed and a new BPL may be established. If the UE cannot detect any response within a specific time period, the UE may perform a retransmission of the request. If the UE cannot detect any response after a specified number of retransmissions, then the UE may notify higher layers, potentially leading to RLF and cell reselection.

According to embodiments of the present disclosure, a UE may declare its capability of supporting BFR for one or more SCells via signaling to a PCell. For example, the UE may indicate whether or not the UE supports BFR for any SCells, a maximum number of SCells for which the UE supports BFR (e.g., simultaneously), and/or whether the UE supports sending BFR requests via PUCCH signaling. In some embodiments, rather than separately indicating whether the UE supports BFR for any SCells and a maximum number of SCells for which the UE supports BFR, the UE may indicate no support of BFR by indicating a maximum number of SCells for which the UE supports BFR to be 0, and indicate the UE supports BFR by indicating a maximum number of SCells for which the UE supports BFR to be greater than 0.

Sending this capability information to the PCell allows the PCell to be aware of the UE's capability with regard to BFR, thereby avoiding duplicative monitoring of SCells by the PCell. Furthermore, receiving the maximum number of SCells for which the UE supports BFR allows the PCell to configure different SR (e.g., PUCCH) to identify which SCell has a beam failure. In an embodiment, the PCell configures, for use by the UE, an SR for each SCell for which the UE supports BFR. As such, if the UE sends a BFR request via a given SR (e.g., SR1), the PCell can determine that a given SCell (e.g., SCell1) that corresponds to the given SR has the beam failure. In these embodiments, the UE may not need to indicate which SCell has the beam failure in a BFR request, as the SR used to send the BFR request indicates the SCell.

Example Operations for Signaling UE Capability for SCell BFR

FIG. 10 is a flow diagram illustrating example operations 1000 for wireless communication by a UE, in accordance with certain aspects of the present disclosure. The operations 1000 may be performed, for example, by a UE 120 to signal capability of the UE for SCell BFR.

Operations 1000 begin, at 1002, by reporting, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells).

At 1004, the UE detects a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells.

At 1006, the UE performs a BFR in accordance with the reported capability, in response to the detection.

FIG. 11 is a flow diagram illustrating example operations 1100 for wireless communication by a network entity, and may be considered complementary to operations 1000 of FIG. 10 . For example, Operations 1100 may be performed, for example, by a BS 110 (e.g., a gNB) to perform actions related UE capability for SCell BFR.

Operations 1100 begin, at 1102, by receiving, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells).

At 1104, the network entity receives, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells.

At 1106, the network entity takes action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure.

UE capability signaling for SCell BFR in accordance with operations 1000 and 1100 of FIGS. 10 and 11 may be understood with reference to the example flow diagram of FIG. 12 .

As illustrated in FIG. 12 , a UE may first send capability information for SCell BFR to a network entity (e.g., a gNB or RRH). The capability information may include, for example, an indication of whether the UE supports SCell BFR, a maximum number of SCells for which the UE supports BFR, and/or an indication of whether the UE has the capability to send BFR requests via PUCCH signaling. In some embodiments, the UE indicates no BFR capability by sending a value of 0 for the maximum number of SCells for the UE supports BFR.

The UE then receives BFD RS from the SCell. In some embodiments, beam failure detection is triggered if a quality metric of reference signals is above or below a threshold. The UE detects a BFD based on the BFD RS from the SCell.

To recover the Scell, the UE sends a beam failure request (BFRQ) message to the PCell. In some embodiments, a two-step BFRQ may be used. The BFRQ may request a new transmission. In some embodiments, the UE sends a scheduling request (SR) and/or a PUSCH including a MAC-CE. The MAC-CE may include an index of the failed CC and/or a new recovery beam candidate beam. In alternative embodiments, the UE does not indicate an index of the failed CC, as this may be indicated by the SR used to send the BFRQ. In some examples, to find candidate new beams, the UE may monitor a beam identification reference signal. In certain embodiments, the BFR request is sent va PUCCH signaling.

The PCell responds to the BFR request with an acknowledgment. In some embodiments, the PCell transmits a beam failure recovery response (BFRR) message to the UE. The BFRR message may acknowledge the MAC-CE and include an uplink grant scheduling a new transmission. For example, the uplink grant may schedule a transmission for the same HARQ process as the PUSCH carrying the MAC-CE in the step two of the BFRQ. In some examples, the BFRR is sent over a CORESET (e.g., referred to as a CORESET-BFR) the UE monitors for the response. If the response is received successfully, the beam recovery is completed and a new BPL may be established. If the UE cannot detect any response within a specific time period, the UE may perform a retransmission of the request. If the UE cannot detect any response after a specified number of retransmissions, then the UE may notify higher layers, potentially leading to RLF and cell reselection.

While some embodiments involve the UE signaling a candidate beam for recovery, the other embodiments involve the PCell selecting a candidate beam for recovery and/or triggering a process by which a candidate beam may be selected.

FIG. 13 illustrates an example 1300 of UE capability signaling for SCell BFR. The example capability signaling indicates: 1) whether the UE supports SCell BFR; 2) a maximum number of SCells configured for BFR; and 3) whether the UE has the capability to send a BFR request via PUCCH signaling. It is noted that some of these indications may be excluded or grouped into a single indication. For example, whether the UE supports SCell BFR may be indicated by whether the maximum number of SCells for which the UE supports BFR is 0 or some other number.

FIG. 14 illustrates a communications device 1400 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in FIG. 10 . The communications device 1400 includes a processing system 1402 coupled to a transceiver 1408 (e.g., a transmitter and/or a receiver). The transceiver 1408 is configured to transmit and receive signals for the communications device 1400 via an antenna 1410, such as the various signals as described herein. The processing system 1402 may be configured to perform processing functions for the communications device 1400, including processing signals received and/or to be transmitted by the communications device 1400.

The processing system 1402 includes a processor 1404 coupled to a computer-readable medium/memory 1412 via a bus 1406. In certain aspects, the computer-readable medium/memory 1412 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 1404, cause the processor 1404 to perform the operations illustrated in FIG. 10 or other operations for performing the various techniques discussed herein for wireless communications by a user equipment (UE). In certain aspects, computer-readable medium/memory 1412 stores code 1414 for reporting, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); code 1416 for detecting a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and code 1418 for performing a BFR in accordance with the reported capability, in response to the detection. In certain aspects, each of code 1414-1418 may be considered means for performing the function indicated.

In certain aspects, the processor 1404 has circuitry configured to implement the code stored in the computer-readable medium/memory 1412. The processor 1404 includes circuitry 1420 for reporting, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); circuitry 1424 for detecting a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and circuitry 1426 for performing a BFR in accordance with the reported capability, in response to the detection. In certain aspects, each of circuitry 1420-1426 may be considered means for performing the function indicated.

FIG. 15 illustrates a communications device 1500 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in FIG. 11 . The communications device 1500 includes a processing system 1502 coupled to a transceiver 1508 (e.g., a transmitter and/or a receiver). The transceiver 1508 is configured to transmit and receive signals for the communications device 1500 via an antenna 1510, such as the various signals as described herein. The processing system 1502 may be configured to perform processing functions for the communications device 1500, including processing signals received and/or to be transmitted by the communications device 1500.

The processing system 1502 includes a processor 1504 coupled to a computer-readable medium/memory 1512 via a bus 1506. In certain aspects, the computer-readable medium/memory 1512 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 1504, cause the processor 1504 to perform the operations illustrated in FIG. 11 or other operations for performing the various techniques discussed herein for wireless communications by a network entity. In certain aspects, computer-readable medium/memory 1512 stores code 1514 for receiving, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); code 1516 for receiving, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and code 1518 for taking action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure. In certain aspects, each of code 1514-1518 may be considered means for performing the function indicated.

In certain aspects, the processor 1504 has circuitry configured to implement the code stored in the computer-readable medium/memory 1512. The processor 1504 includes circuitry 1520 for receiving, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); circuitry 1524 for receiving, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and circuitry 1526 for taking action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure. In certain aspects, each of circuitry 1520-1526 may be considered means for performing the function indicated.

Example Clauses

Implementation examples are described in the following numbered clauses:

Clause 1: A method for wireless communications by a user equipment (UE), comprising: reporting, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); detecting a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and performing a BFR in accordance with the reported capability, in response to the detection.

Clause 2: The method of Clause 1, wherein reporting the capability comprises: reporting a maximum number of SCells for which the UE can support BFR.

Clause 3: The method of Clause 2, wherein the maximum number of SCells for which the UE can support BFR comprises a maximum number of SCells for which the UE can support BFR simultaneously.

Clause 4: The method of any of Clause 2-3, wherein a particular value is reported to indicate no support for BFR on the one or more SCells.

Clause 5: The method of any of Clause 1-4, wherein reporting the capability comprises: reporting a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.

Clause 6: The method of Clause 5, wherein performing the BFR in accordance with the reported capability, comprises sending a BFR request via a PUCCH transmission.

Clause 7: The method of Clause 6, wherein the BFR request indicates a candidate beam to replace a failed beam.

Clause 8: The method of any of Clause 6-7, further comprising receiving an acknowledgment of the BFR request from the network entity.

Clause 9: A method for wireless communication by a network entity, comprising: receiving, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); receiving, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and taking action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure.

Clause 10: The method of Clause 9, wherein the indication of the capability comprises: an indication of a maximum number of SCells for which the UE can support BFR.

Clause 11: The method of Clause 10, wherein the maximum number of SCells for which the UE can support BFR comprises a maximum number of SCells for which the UE can support BFR simultaneously.

Clause 12: The method of any of Clause 10-11, wherein a particular value is reported to indicate no support for BFR on the one or more SCells.

Clause 13: The method of any of Clause 9-12, wherein the indication of the capability comprises: an indication of a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.

Clause 14: The method of Clause 13, wherein receiving the indication of the detected beam failure comprises receiving an indication of the detected beam failure via a BFR request.

Clause 15: The method of Clause 14, wherein the BFR request is received via a PUCCH transmission.

Clause 16: The method of any of Clause 14-15, wherein the BFR request indicates a candidate beam to replace a failed beam.

Clause 17: An apparatus for wireless communications by a user equipment (UE), comprising: a memory; and a processor coupled to the memory, the memory and processor configured to: report, to a network entity, a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); detect a beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and perform a BFR in accordance with the reported capability, in response to the detection.

Clause 18: The apparatus of Clause 17, wherein reporting the capability comprises: reporting a maximum number of SCells for which the UE can support BFR.

Clause 19: The apparatus of Clause 18, wherein the maximum number of SCells for which the UE can support BFR comprises a maximum number of SCells for which the UE can support BFR simultaneously.

Clause 20: The apparatus of any of Clause 18-19, wherein a particular value is reported to indicate no support for BFR on the one or more SCells.

Clause 21: The apparatus of any of Clause 17-20, wherein reporting the capability comprises: reporting a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.

Clause 22: The apparatus of Clause 21, wherein performing the BFR in accordance with the reported capability, comprises sending a BFR request via a PUCCH transmission.

Clause 23: The apparatus of Clause 22, wherein the BFR request indicates a candidate beam to replace a failed beam.

Clause 24: An apparatus for wireless communications by a network entity, comprising: a memory; and a processor coupled to the memory, the memory and processor configured to: receive, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on one or more secondary cells (SCells); receive, from the UE, an indication of a detected beam failure of a beam pair link (BPL) associated with an Scell of the one or more SCells; and take action to initiate a BFR in accordance with the reported capability, in response to the receiving the indication of the detected beam failure.

Clause 25: The apparatus of Clause 24, wherein reporting the capability comprises: reporting a maximum number of SCells for which the UE can support BFR.

Clause 26: The apparatus of Clause 25, wherein the maximum number of SCells for which the UE can support BFR comprises a maximum number of SCells for which the UE can support BFR simultaneously.

Clause 27: The apparatus of any of Clause 25-26, wherein a particular value is reported to indicate no support for BFR on the one or more SCells.

Clause 28: The apparatus of any of Clause 24-27, wherein reporting the capability comprises: reporting a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.

Clause 29: The apparatus of Clause 28, wherein performing the BFR in accordance with the reported capability, comprises sending a BFR request via a PUCCH transmission.

Clause 30: The apparatus of Clause 29, wherein the BFR request indicates a candidate beam to replace a failed beam.

Clause 31: A processing system for wireless communication, comprising: a memory comprising computer-executable instructions; one or more processors configured to execute the computer-executable instructions and cause the processing system to perform a method in accordance with any one of Clauses 1-16.

Clause 32: An apparatus for wireless communication, comprising means for performing a method in accordance with any one of Clauses 1-16.

Clause 33: A non-transitory computer-readable medium for wireless communication comprising computer-executable instructions that, when executed by one or more processors of a processing system, cause the processing system to perform a method in accordance with any one of Clauses 1-16.

Clause 34: A computer program product for wireless communication embodied on a computer-readable storage medium comprising code for performing a method in accordance with any one of Clauses 1-16.

The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal 120 (see FIG. 1 ), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media). In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal). Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein. For example, instructions for performing the operations described herein and illustrated in FIGS. 10-11 .

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims. 

What is claimed is:
 1. A method for wireless communications by a user equipment (UE), comprising: reporting, to a base station, a capability of the UE to support beam failure recovery (BFR) on a plurality of secondary cells (SCells), wherein reporting the capability comprises reporting a maximum number of SCells for which the UE can support BFR simultaneously; detecting two or more beam failures of two or more beam pair links (BPLs) associated with two or more Scells of the plurality of SCells; and performing a BFR with respect to the two or more Scells simultaneously in accordance with the reported capability, in response to the detection.
 2. The method of claim 1, wherein a particular value is reported to indicate no support for BFR.
 3. The method of claim 1, wherein reporting the capability comprises: reporting a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.
 4. The method of claim 3, wherein performing the BFR in accordance with the reported capability, comprises sending a BFR request via a PUCCH transmission.
 5. The method of claim 4, wherein the BFR request indicates a candidate beam to replace a failed beam.
 6. The method of claim 4, further comprising receiving an acknowledgment of the BFR request from the base station.
 7. A method for wireless communication by a base station, comprising: receiving, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on a plurality of secondary cells (SCells), wherein the indication of the capability comprises an indication of a maximum number of SCells for which the UE can support BFR simultaneously; receiving, from the UE, indications of two or more detected beam failures of two or more beam pair links (BPLs) associated with two or more Scells of the plurality of SCells; and performing one or more actions to initiate a BFR with respect to the two or more Scells simultaneously in accordance with the reported capability, in response to the receiving the indications of the two or more detected beam failures, wherein the one or more actions comprise transmitting, to the UE, one or more uplink grants scheduling one or more new transmissions, wherein two or more new BPLs are established based on the one or more new transmissions to replace the two or more BPLs that failed.
 8. The method of claim 7, wherein a particular value is reported to indicate no support for BFR.
 9. The method of claim 7, wherein the indication of the capability comprises: an indication of a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.
 10. The method of claim 9, wherein receiving the indications of the two or more detected beam failures comprises receiving one or more BFR requests.
 11. The method of claim 10, wherein the one or more BFR requests are received via a PUCCH transmission.
 12. The method of claim 10, wherein the one or more BFR requests indicate a candidate beam to replace a failed beam.
 13. An apparatus for wireless communications by a user equipment (UE), comprising: a memory; and a processor coupled to the memory, the memory and processor configured to: report, to a base station, a capability of the UE to support beam failure recovery (BFR) on a plurality of secondary cells (SCells), wherein reporting the capability comprises reporting a maximum number of SCells for which the UE can support BFR simultaneously; detect two or more beam failures of two or more beam pair links (BPLs) associated with two or more Scells of the plurality of SCells; and perform a BFR with respect to the two or more Scells simultaneously in accordance with the reported capability, in response to the detection.
 14. The apparatus of claim 13, wherein a particular value is reported to indicate no support for BFR.
 15. The apparatus of claim 13, wherein reporting the capability comprises: reporting a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.
 16. The apparatus of claim 15, wherein performing the BFR in accordance with the reported capability, comprises sending a BFR request via a PUCCH transmission.
 17. The apparatus of claim 16, wherein the BFR request indicates a candidate beam to replace a failed beam.
 18. An apparatus for wireless communications by a base station, comprising: a memory; and a processor coupled to the memory, the memory and processor configured to: receive, from a user equipment (UE), an indication of a capability of the UE to support beam failure recovery (BFR) on a plurality of secondary cells (SCells), wherein the indication of the capability comprises an indication of a maximum number of SCells for which the UE can support BFR simultaneously; receive, from the UE, indications of two or more detected beam failures of two or more beam pair links (BPLs) associated with two or more Scells of the plurality of SCells; and perform one or more actions to initiate a BFR with respect to the two or more Scells simultaneously in accordance with the reported capability, in response to the receiving the indications of the two or more detected beam failures, wherein the one or more actions comprise transmitting, to the UE, one or more uplink grants scheduling one or more new transmissions, wherein two or more new BPLs are established based on the one or more new transmissions to replace the two or more BPLs that failed.
 19. The apparatus of claim 18, wherein a particular value is reported to indicate no support for BFR.
 20. The apparatus of claim 18, wherein the indication of the capability comprises: an indication of a capability of the UE to send a BFR request via a physical uplink control channel (PUCCH) transmission.
 21. The apparatus of claim 20, wherein receiving the indications of the two or more detected beam failures comprises receiving one or more BFR requests.
 22. The apparatus of claim 21, wherein the one or more BFR requests indicate a candidate beam to replace a failed beam. 